#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

int main(void){
  int k, n; cin >> k >> n;
  vector<bool> exi(10, false);
  int nn=n;
  vector<int> yakusu(nn+1, -1), prime;
  for(int i=2; i<=nn; i++){
    if(yakusu[i]!=-1) continue;
    int copy=i;
    prime.push_back(i);
    while(copy<=nn){
      if(yakusu[copy]==-1) yakusu[copy]=i;
      copy+=i;
    }
  }
  auto f=[&](auto f, int now){
    int copy=now, ans=0;
    while(copy){
      ans+=copy%10; copy/=10;
    }
    if(ans<10) return ans;
    else return f(f, ans);
  };
  int left=lower_bound(prime.begin(), prime.end(), k)-prime.begin();
  int maxi=-1, right=left, m=prime.size(), ansleft;
  vector<int> hash;
  for(auto p:prime) hash.push_back(f(f, p));
  while(left<m&&prime[left]<=n){
    if(left>right) right=left;
    while(right<m){
      if(exi[hash[right]]) break;
      else exi[hash[right]]=true, right++;
    }
    if(maxi<=right-left) maxi=right-left, ansleft=prime[left];
    if(right>=m) break;
    exi[hash[left]]=false; left++;
  }
  cout << ansleft << endl;
  return 0;
}